THEY zip around on flashy motorcycles, race each other and talk for hours about their beloved two-wheelers over beer.

But motorcycle gangs, or Mat Rempit, are fast losing their fairly tame image here as a more sinister picture emerges.

Last month, six members of the Onyx gang were jailed and caned for killing a 46-year-old technician from a rival gang. Three members are still on the run.

Prosecutors called the crime the "most horrific gang killing in recent years".

That vicious assault in Central Square in September last year - which left the victim with at least 78 wounds - was not an isolated gang clash.

The police said bike gangs in recent years have been involved in a "handful" of illegal incidents such as fighting in public.

They did not give details on how many such cases there have been, but a spokesman said they have increased enforcement action against them.

Some gang members of several bike gangs told The Sunday Times of a violent incident last month when a member's wedding led to a fist-fight with a motorist who had been stuck in traffic because of the convoy of about 100 bikes following the wedding motorcycle.

Bike gangs have been around for more than 20 years. They started as peaceful groups of pals with a common interest in bikes.

They would attend race events overseas and undertake long-distance road trips to Malaysia and Thailand.

Back then, there were only about 10 gangs, but this figure has since grown to at least 20.

Most have only about 20 members each, although the more established ones boast of at least 50.

Members pay a monthly fee which goes into printing T-shirts and organising trips.

Some of the better known gangs here are Teratai, Alif, Blackjack and Phantom.

Members are easily identified by the unique logo on their helmets while some have T-shirts bearing the gang's logo and sometimes a catchy slogan.

One uses an eagle, another a leaping tiger while one has a flower as the gang symbol.

A few of the newer gangs use simpler designs such as stripes or checks to set themselves apart from the veterans.

A person can join a gang if he owns the same brand of bike as the others.

Some gangs require newbies to pass an initiation test - often in the form of a bike race against other members to see if they can be an asset to the group.

A gang member from Teratai, who has been in gangs for over 10 years, said new members, who are usually in their 20s, have been the reason the gangs get involved in scuffles more often.

"They get angry easily and start fights just because they lose a race to another gang," he said. "Losing a race is already bad enough, but they cannot stand losing face."

More stand-offs occur nowadays, too, because younger members like bringing their girlfriends along on their bikes to show off.

Tempers flare when rival gang members make fun of their motorcycles, riding skills or their girls.

Many new members are also from secret societies such as Omega, he added.

The technician who was beaten and stabbed to death last year, Mr Zainal Nek, was said to be from the Blackjack motorcycle gang.

The men who attacked him were looking for the Alif gang for a "showdown" after its members beat up one of their guys.

But they could not find them, and instead chanced upon Mr Zainal, whom they recognised as the second-in-command in the Blackjack gang, which had close links to Alif.

Such incidents have put gangs on the police's radar, including the Secret Societies Branch, said a senior member of a gang that hangs out in Bukit Batok.

He said officers have stopped to question his members even if they are just having dinner at coffee shops.

He said: "Most of us just want to have fun with our bikes. The police attention is very bad for us."